Thickness and strain dependence of piezoelectric coefficient in ${\mathrm{BaTiO}}_3$ thin films

Journal Article · 11 February 2020 · Physical Review Materials

DOI: https://doi.org/10.1103/PhysRevMaterials.4.024407 · OSTI ID:1599490

Kelley, K. P.; Yilmaz, D. E.; Collins, L.; Sharma, Y. ; Lee, H. N.; Akbarian, D.; van Duin, A. C. T.; Ganesh, P.; Vasudevan, R. K.

We explore the thickness dependence of the converse piezoelectric coefficient (d₃₃) in epitaxial thin films of BaTiO₃ (BTO) grown on (001) SrTiO₃ substrates. Piezoresponse force microscope was performed using an atomic force microscope equipped with an interferometric displacement sensor allowing direct quantification of electromechanical coupling coefficients in BTO free from unwanted background contributions. We find that 80-nm-thick films exhibit a d₃₃ of ~20.5pm/V, but as the thickness is reduced, the d₃₃ reduces to less than 2 pm/V for a 10 nm film. To explain the atomistic origin of the effect, we performed molecular dynamics simulations with a recently developed ab initio-derived reactive force field, constructed using the ReaxFF framework. Simulations predict that under applied electric fields thin films of BaTiO₃ show an increasing thickness, with compressive strain, of the region screening the depolarization-field. This study confirms quantitatively the drop in piezoelectric performance in BTO ultrathin films and again highlights the importance of the screening mechanisms when films approach the ultrathin limits in dictating the functional behaviors.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)
• Sponsoring Organization: US Air Force Office of Scientific Research (AFOSR); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
• Grant/Contract Number: AC02-05CH11231; AC05-00OR22725
• OSTI ID: 1599490
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 2 Vol. 4; ISSN PRMHAR; ISSN 2475-9953
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English